From 41bc48c79195f018687fef2ba64e4c87bb7a206b Mon Sep 17 00:00:00 2001
From: Michael Andreen <harv@ruin.nu>
Date: Wed, 15 Mar 2006 12:35:18 +0000
Subject: [PATCH] more generic type declaration and evaluates input directly

---
 Interpret.hs | 59 +++++++++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/Interpret.hs b/Interpret.hs
index 948903e..5e18d88 100644
--- a/Interpret.hs
+++ b/Interpret.hs
@@ -21,19 +21,21 @@ type Function = ([Decl],[Stm])
 
 data State = State {variables::Variables,functions::(Map Ident Function),ret::Value}
 
-type EvalM = ErrorT String (StateT State IO)
+type EvalM m = ErrorT String m
 
 interpret :: [Func] -> [Stm] -> IO ()
 interpret fun st = do
-	runStateT (runErrorT  (do mapM Interpret.addFunction fun; mapM_ execute st)) emptyState
+	runStateT (runErrorT  (do mapM addFunction fun; mapM_ execute st)) emptyState
 	return ()
 
---eval :: (MonadState Variables m) => Exp -> m Value
-eval :: Exp -> EvalM Value
+--eval :: (MonadState State m, MonadError String m, MonadIO m) => Exp -> m Value
+eval :: (MonadState State m, MonadIO m) => Exp -> EvalM m Value
 eval (EBool b) = return (VBool b)
 eval (EInt n) = return (VInt n)
 eval (EVar i) = getVariableValue i
-eval (EAss i e) = setVariableValue i e
+eval (EAss i e) = do 
+	v <- eval e
+	setVariableValue i v
 eval (BiOpExp e o e') = do
 	v <- eval e
 	v'<- eval e'
@@ -41,7 +43,7 @@ eval (BiOpExp e o e') = do
 		else let (VInt n1) = v in let (VInt n2) = v' in return $ op o n1 n2
 eval (EPost i o) = do
 	(VInt n) <- getVariableValue i
-	let (VInt n') = op o n 1 in setVariableValue i $ EInt n'
+	setVariableValue i $ op o n 1
 	return $ VInt n
 eval (ENeg e) = do
 	(VInt n) <- eval e
@@ -50,10 +52,10 @@ eval (ENot e) = do
 	(VBool b) <- eval e
 	return $ VBool $ not b
 eval EReadI = do
-	s <- liftIO $ getWord
+	s <- liftIO $ getNumber
 	return $ VInt $ read s
 eval EReadB = do
-	s <- liftIO $ getWord
+	s <- liftIO $ getNumber
 	return $ VBool $ if (read s == 0) then False else True
 eval (EFunc i as) = do
 	vs <- mapM eval as
@@ -61,19 +63,30 @@ eval (EFunc i as) = do
 	(ds,ss) <- lookup i $ functions state
 	let m = foldr (\((Decl t i),v) m -> insert i v m) empty $ zip ds vs
 		in modify (\s -> s{variables=[m]})
-	mapM_ execute ss `catchError` (\_ -> return ())
-	s <- get
+	(mapM_ execute ss >> (fail $ "Function "++show i++" didn't return anything."))
+		`catchError` (\_ ->return ()) --Only errors thrown in ErrorT can be caught here, runtime errors pass through, so no need to check the error
+	state' <- get
 	put state
-	return $ ret s
+	return $ ret state'
+
+--Stricter evaluation of the input
+getNumber :: IO String
+getNumber = do
+	c <- getChar
+	if elem c ['-','0'..'9']
+		then do
+			l <- getNumber2
+			return (c:l)
+		else fail "Non integer input."
 
-getWord :: IO String
-getWord =  do
+getNumber2 :: IO String
+getNumber2 =  do
 	c <- getChar
-	if elem c [' ', '\n', '\t', '\r']
-		then return ""
-		else do
-			l <- getWord
+	if elem c ['0'..'9']
+		then do
+			l <- getNumber2
 			return (c:l)
+		else return ""
 
 -- op :: Op -> (a -> a -> Value)
 opE Eq = \e e' -> VBool $ e == e'
@@ -92,15 +105,13 @@ getVariableValue i = do
 	s <- get 
 	findVariable i $ variables s
 
-findVariable :: (MonadState State m) => Ident -> Variables -> m Value
+findVariable :: (Monad m) => Ident -> Variables -> m Value
 findVariable i [] = fail $ "Variable "++show i++" not found in any scope."
 findVariable i (m:ms) = if member i m then lookup i m else findVariable i ms
 
-setVariableValue :: Ident -> Exp -> EvalM Value
-setVariableValue i e = do
-	v <- eval e
-	state <- get
-	modify (\s -> s{variables= updateVariable i v $ variables state} )
+setVariableValue :: (MonadState State m) => Ident -> Value -> EvalM m Value
+setVariableValue i v = do
+	modify (\s -> s{variables= updateVariable i v $ variables s} )
 	return v
 
 updateVariable :: Ident -> Value -> Variables -> Variables 
@@ -114,7 +125,7 @@ pushAndPop s = do
 	modify (\s -> s { variables = tail $ variables s})
 
 -- execute :: (MonadState Variables m) => Stm -> m ()
-execute :: Stm -> EvalM ()
+execute :: (MonadState State m, MonadIO m) => Stm -> EvalM m ()
 execute (SNoop) = return ()
 execute (SExp e) = eval e >> return ()
 execute (SIf b s s') = do
-- 
2.39.2